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Airspace and charts
Latitude, longitude, scale and MEF on a sectional chart
A sectional uses a 1:500,000 scale, so 1 inch is 6.86 nautical miles (about 8 statute miles). Parallels of latitude run east-west and meridians of longitude run north-south, and each 30 minute by 30 minute quadrant carries a Maximum Elevation Figure in hundreds of feet MSL.
How do latitude and longitude lines work on a sectional?
The study guide explains the grid in terms of the Earth. Circles parallel to the equator, the lines that run east and west, are parallels of latitude. They measure degrees north or south of the equator, up to 90 degrees at the pole. Meridians of longitude run from pole to pole at right angles to the equator and measure degrees east or west of the Prime Meridian, which passes through Greenwich, England, out to 180 degrees.
For the 48 contiguous states the study guide gives the ranges: between 25 and 49 degrees N latitude and between 67 and 125 degrees W longitude. Two of its sample points are Washington, D.C., at approximately 39 N, 77 W and Chicago at approximately 42 N, 88 W.
| Line type | Runs | Measures | US values |
|---|---|---|---|
| Parallel of latitude | East and west | Degrees north of the equator | About 25 to 49 N |
| Meridian of longitude | North and south | Degrees west of Greenwich | About 67 to 125 W |
Because the US is in the western hemisphere, longitude numbers get larger as you move west, toward the left of a north-up chart. Latitude numbers get larger as you move north, toward the top. That is why 42 N, 88 W (Chicago) sits above and to the left of 39 N, 77 W (Washington).
Sources (checked 2026-11-14): FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22); FAA Pilot's Handbook of Aeronautical Knowledge.
How do I find a point from its coordinates?
Work one axis at a time. First find the line or tick for the latitude and trace it across the chart. Then find the longitude and trace it up or down. The point is where they cross. The Chart Users' Guide describes the ticked lines that divide each 30 minutes of latitude and longitude on a sectional; those 30 minute marks give you a fast way to narrow down which box holds the point.
Worked example
Placing a point in its quadrant
Say you are given 39 degrees 15 minutes N and 77 degrees 45 minutes W. This is a made-up point near the Washington, D.C. example above.
- Latitude: 39 degrees 15 minutes lies between 39 00 and 39 30 N, so it is in the southern half of that degree band.
- Longitude: 77 degrees 45 minutes lies between 77 30 and 78 00 W. Because longitude increases to the west, it is in the western half of the 77 degree band, closer to the 78 degree line.
- The point sits in the quadrant bounded by 39 00 to 39 30 N and 77 30 to 78 00 W. Read that quadrant's MEF for terrain and obstacle information.
If the question gives a sample like 42 N, 88 W, you know the point is north of 39 N and west of 77 W, so it plots above and to the left of the D.C. sample.
Sources (checked 2026-11-14): FAA Aeronautical Chart Users' Guide (effective 9 July 2026); FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22).
What does the 1:500,000 scale mean for measuring distance?
The study guide states the sectional scale as 1:500,000, with 1 inch equal to 6.86 nautical miles (NM), or approximately 8 statute miles (SM). One inch on the chart is 500,000 inches on the ground. The arithmetic is quick: 500,000 inches is about 41,667 ft, and dividing by 6,076 ft per NM gives 6.86 NM.
| Chart distance | Ground distance (NM) | About (SM) |
|---|---|---|
| 0.5 inch | 3.43 | 3.9 |
| 1 inch | 6.86 | 7.9 |
| 2.5 inches | 17.15 | 19.7 |
| 5 inches | 34.3 | 39.5 |
Worked example
A 5 NM core on paper
The AIM says a typical Class C surface core has a 5 NM radius and the shelf has a 10 NM radius. On a sectional that is 5 / 6.86, or about 0.73 inch, for the core and 10 / 6.86, or about 1.46 inches, for the shelf. If you measure 2 inches from an airport symbol to your job site, you are about 13.7 NM out, which is outside both rings of a typical Class C.
Use the scale bar printed on the chart as a cross check. Several things trip people up: a statute mile is shorter than a nautical mile, so 8 SM per inch is a rounded figure, and a scale does not carry across chart types. The Chart Users' Guide gives Terminal Area Charts a scale of 1:250,000, half the sectional's, so one inch on a TAC is about 3.43 NM. The PSI bulletin says you may bring your own rulers, plotters and similar tools to the test, subject to its rules. If you do not have a plotter, a plain ruler and the arithmetic above work: multiply inches by 6.86 for nautical miles, or by about 8 for a quick statute mile estimate.
Sources (checked 2026-11-14): FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22); AIM 3-2: Controlled Airspace; FAA Aeronautical Chart Users' Guide (effective 9 July 2026); PSI UAG Information Bulletin (effective 29 Sep 2025).
What is a Maximum Elevation Figure (MEF)?
The Chart Users' Guide defines the MEF as the highest elevation within a quadrant, including terrain and other vertical obstacles such as towers and trees. A sectional quadrant is the area bounded by the ticked lines dividing each 30 minutes of latitude and each 30 minutes of longitude. The figure is rounded up to the next 100 ft, and the last two digits are not shown, so a printed 28 means 2,800 ft MSL.
The guide's own man-made obstacle example shows how it is built: an obstacle top at 2,649 ft MSL, plus 100 ft of possible vertical error, gives 2,749, which is raised to the next hundred, 2,800 ft, and printed as 28. The guide cautions that the MEF is based on the best information available to the specialist, so it is an estimate and not a guarantee.
Worked example
Using an MEF to bound the ground
Say the quadrant over your site shows a large 28. Nothing in that quadrant, terrain or obstacle, is higher than 2,800 ft MSL as charted. So the ground under you is at most 2,800 ft MSL, and a drone at 400 ft AGL is at most 3,200 ft MSL. If a controlled-airspace shelf begins at 3,300 ft MSL (charted as 33), you can be sure from the MEF alone that a 400 ft flight stays beneath it. If the shelf began at 3,000 ft MSL, the MEF alone would not settle it, and you would look for a spot elevation or contour to pin down the ground at your site.
The MEF is also the reason a drone pilot sees a number that seems too high. It reflects the tallest tower in the quadrant, not the ground where you stand. Use it as an upper bound only.
Sources (checked 2026-11-14): FAA Aeronautical Chart Users' Guide (effective 9 July 2026).
How do I know the chart is current?
The FAA's VFR chart page lists each sectional with a current and a next edition date. When checked on 2026-11-14, the current edition date was 29 October 2026 and the next was 24 December 2026, which is 56 days later. The Chart Users' Guide says these charts are updated every 56 days, tells you to check the effective dates on each chart and publication, and says to confirm currency by looking at the next scheduled effective date printed on the cover. It also tells pilots to check NOTAMs for updates that arrive between chart cycles.
The Remote Pilot Study Guide's chapter on sectionals still says the charts are revised semiannually. That wording is older than the current 56 day schedule, so for real flights trust the effective dates on the chart itself. The FAA also publishes the next edition 20 days before its effective date.
Sources (checked 2026-11-14): FAA VFR charts page (current and next editions); FAA Aeronautical Chart Users' Guide (effective 9 July 2026); FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22).
What are the common test traps with scale, coordinates and MEF?
- Mixing nautical and statute miles. The scale gives 6.86 NM per inch. 8 SM per inch is the rounded statute equivalent.
- Reading longitude the wrong way. In the US, longitude values grow toward the west, which is the left side of the chart.
- Dropping the zeros off an MEF. A printed 28 is 2,800 ft MSL.
- Treating the MEF as the ground elevation. It is the highest point in a 30 by 30 minute quadrant, including obstacles.
- Using an old chart. The legend date and the 56 day cycle decide whether a chart is usable. The same cadence applies to the Chart Supplement.
Use the shelf labels on the same chart together with the MEF and spot elevations: see Class C for converting a shelf floor from MSL to AGL, and the free chart lessons for practice.
Related guides
- How to read airspace classes on a sectional chart
- Class C airspace for drone pilots
- How to read an airport entry in the Chart Supplement
- Free sectional chart practice
- The FAA testing supplement for Part 107: figures, legends and the October 2026 change
- All Part 107 guides
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Sources
- FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22), checked 2026-11-14
- FAA Aeronautical Chart Users' Guide (effective 9 July 2026), checked 2026-11-14
- FAA VFR charts page (current and next editions), checked 2026-11-14
- AIM 3-2: Controlled Airspace, checked 2026-11-14
- FAA Pilot's Handbook of Aeronautical Knowledge, checked 2026-11-14
- PSI UAG Information Bulletin (effective 29 Sep 2025), checked 2026-11-14
How this page was made: written by Certloom Learning from the sources above, with the rules checked against the current regulation text. Practice items are original questions from the app's reviewed bank. Spot an error? certloomlearning@gmail.com.